Explosive composition containing aluminum,potassium perchlorate,and sulfur or red phosphorus



United States Patent cc 3,437,534 EXPLOSIVE COMPOSITION CONTAININGALUMI- N UM, POTASSIUM PERCHLORATE, AND SUL- FUR OR RED PHOSPHORUSWilliam S. McEwan, China Lake, and Edward W. La Rocca, Miraleste,Califi, assignors to the United States of America as represented by theSecretary of the Navy No Drawing. Filed Nov. 18, 1963, Ser. No. 324,591Int. Cl. C06b 11/00 US. Cl. 149-30 3 Claims The invention hereindescribed may be manufactured and used by or for the Government of theUnited States of America for governmental purposes without the paymentof any royalties thereon or therefor.

The present invention relates to an explosive composition, the productsof which are soluble in water.

In the area of underwater explosive research the characteristics ofexplosion are generally determined by limiting the boundary conditionsfor simplification of the mathematics involved. Two assumptions made arethat generally the gaseous products of detonation do not dissolve inwater to any appreciable extent, and the gaseous products at all timesassume the form of a spherical bubble and behave as a permanent gas. Itis postulated that on detonation of an underwater explosive a shock waveis first produced, then the gaseous products of the explosive expand toform a bubble. Inertial effects cause the bubble to overexpand to a lowpressure, following which the hydrostatic pressure of the surroundingwater recompresses the bubble. This process may repeat itself five orsix times before the bubble breaks up or escapes from the water. A greatamount of the energy of explosion is by this mechanism dissipated in theformation of the bubble and its oscillations. Experimental evidencereveals that approximately 50% of the original energy of the explosiveis stored in the bubble. To avoid this loss research was carried on tofind an explosive which produces condensable products. Systems based onthe conventional CHON explosives are not satisfactory because of theinsoluble gases produced after the detonation. In cases where the amountof gaseous products were a minor fraction of the mass, as inmetal-perchlorate binary systems, the results gave a low yield on acalories/ gram basis. The present invention produces greater energy pergram and the end products (gases or condensable solids) are extremelysoluble in water.

An object of the present invention is to provide an explosive for use inunderwater weapons systems which produce condensable products.

Another object of this invention is to provide an explosive which willproduce a sharply-defined detonation underwater aimed at production of asingle pressure-time pulse with increased explosive-energy yield andpower, and minimum energy loss through bubble formation andosscillation.

Still another object is to provide an explosive for use in crateringoperations.

A further object of the invention is the provision of an explosive withincreased energy yield and power which is inexpensive, efficient,reliable, and stable to high temperatures.

Other objects, features and many of the attendant advantages of thisinvention will become readily appreciated as the same become betterunderstood by reference to the following detailed description.

The underwater explosive composition of this invention consistsessentially of a metallic element or alloy which produces an oxideexothermically, such as aluminum, vanadium, and uranium; a perchloratewhich does not contain a gas forming element selected from the groupcon- Patented Apr. 8, 1969 EXAMPLE I Ingredients: Percent by weightAluminum 18.3 Sulfur 14.6 Potassium perchlorate 67.1

The above ingredients were dry blended for about onehalf hour. Everyprecaution must be taken to prevent the accumulation and discharge ofcharges of static electricity as the dust produced within the blendermakes it hazardous. The thoroughly mixed composition is then transferredto airtight containers for temporary storage.

The composition may be wet mixed using hexane or other suitable liquidcompatible with the ingredients. The weighed ingredients are placed in apan with sufiicient liquid to form a thick paste. The material is mixeduntil the composition becomes sufficiently granular to be screened butis not dry. The time required for this is from 20 minutes to two hours.The mixture is then granulated by screening, dried at about C. in anoven and transferred to an airtight container.

The potassium perchlorate used herein was sufiiciently fine to passthrough 325 mesh. The sulfur was sublimed flowers of sulfur with ascreen mesh size varying from to 325. Two grades of aluminum were used;namely, flake aluminum of 100 mesh size and atomized aluminum with amesh size ranging from 100 to 325.

In order to determine the chemical stability, the above formulation washeated to a temperature of 300 C. and the only reaction recorded was anendothermic reaction between 100 and C. This was probably due to thechange of state of the sulfur which has a crystalline transition fromrhombic to monoclinic at 9 6 C. and melts at 114.5 C. The furnace wasthen adjusted to permit studies at higher temperature and a secondanalysis was performed. Again, an endothermic reaction occurred justabove 100 C., while a second endothermic reaction with a magnitudenearly eight times the first, started at 300 C. and continued on up to315 C. This excursion possibly resulted from a change of phase inpotassium perchlorate. At approximately 350 C. the reaction slowlystarted going exothermic, the first indication of a chemical reaction inthese tests. At 380 C. this exothermic reaction suddenly accelerated andpeaked at 385 0., though at a relatively low amplitude. Anotherexothermic reaction reached an amplitude about twice that of the formerand peaked at 495 C. A thin stream of white smoke evolved from thesample from 350 C. to 500 C. at which temperature the runs wereterminated. The sample residue was examined after cooling and appearedchanged very little from its initial state. A match was applied to theresidue which ignited readily and burned violently, very similar to theburning of smokeless powder. It appears that very little reactionoccurred up to 500 C. Therefore, it may be concluded that thiscomposition is safe up to 500 C. (in the absence of flame).

The average heat of explosion of this formulation, by calorimeter, was1450 calories/ gram, compared to a computed value of 1690.

A standard Bureau of Explosives drop test apparatus (8 lb. drop weight,7 pellet diameter) was used to test the impact sensitivity of theformulations. Five out of seven samples tested had consistently 50% firelevel at 2 /2 inches. This shows the sensitivity similar to PETN. Allthe tests were made with samples having approximate densities of onegram per cubic centimeter.

3 EXAMPLE II Ingredients: Percent by weight Aluminum 12.09 Phosphorus(red) 17.11 Potassium perchlorate 70.80

The above formulation was dry blended by the same method described inExample .1. Red phosphorus is used because it is safer to handle and itis much less active in its chemical behavior. The aluminum contributesmuch heat to the reaction and the other two products produce the gasnecessary to provide explosive power.

The heat of explosion of the above formulation, by calorimeter, was1844.7 calories per gram. The calculated value was 1878.

The reactions which occur when either of the above formulations aredetonated may be represented as follows:

Perhaps a more meaningful reaction would be the following using theAlSKClO formulation:

Inspection will show that this reaction can be balanced in a number ofways, so long as the oxygen balance is maintained. This requires thator, in other words, the amounts of aluminum and sulfur can be variedindependently and stoichiometry still be obtained by controlling theperchlorate. This system suggests that with the reaction supplying 400Kcal./mole of aluminum trioxide, as much A1 should be formed aspossible, and the number of moles of S0 formed should be as high aspossible to boost the explosive power. To achieve the optimum energyfrom this system, it is necessary to maximize the heat output due toproduct formation and to maximize the gas produced as well. (Theperchlorate and chloride quantities can be neglected because the heatsof formation of these compositions are almost identical and do notcontribute significantly to the overall reaction.) Furtherconsiderations indicate that the initial volume of gas produced is notlimited to S0 or P 0 as the case may be, but includes KCl, also, sinceenough heat is liberated to form gaseous KCI. The total heat of reactionis then given by:

where the negative sign implies an exothermic reaction, and the otherterms are heats of formation in Kcal. and moles.

A function Q is now defined which can be optimized to give a maximum toboth the heat of reaction and the number of gas moles produced. Assumingthe above elementary reactions to occur during the detonation Thisrelation can be optimized by means of the relations between a, b, and c.Differentiating the final expression and solving for a maximum shows apeak in the Q versus a/b curve when the aluminum/sulfur molar ratio is2.053.

These formulations have impact sensitivity results which place themamong the more sensitive secondary explosives on the basis of droptests. Tests were made with samples having approximate densities of onegram per cubic centimeter.

The following table shows the comparison with PETN as the control:

It is apparent from the above that these formulations have a sensitivitycomparable to PETN. The presence of aluminum in the compositiondecreases its sensitivity, althugh aluminum certainly adds to thestrength after detonation gets under way.

The formulations were checked for ignition sensitivity by applying theflame from a wooden match to a small quantity of the mix. The mostsensitive of the tested samples ignited from the flame of a burning woodmatch after being raised to 500 C. and cooled. The violence of burningof this particular sample appeared greater than the other samplestested.

Adding water to the formulations in proportions up to 25% of the mixweight increased the difficulty of ignition in proportion to thepercentage of water. However, once ignition got underway, the mixescontinued burning until consumed, though at a lower rate than the drysamples.

These tests indicated that sufficiently large batches of the compositioncould be safely mixed, handled, and fired to determine critical diameterand other characteristics of these explosives by exercising normalprecautions against heat, sparking, and impact hazards.

Tests were made to determine the critical diameters of theseformulations. In these tests the smallest charge diameter, in whichdetonation was sustained in charge lengths of at least six chargediameters. The following tabulation shows these results as determined tothe nearest /2" charge diameter.

The formulations are listed in order of ascending densities and as mightbe predicted from the behavior of multi-component type explosives (incontrast to monomolecular explosives, e.g., TNT), the sensitivitydecreases with increasing density thereby requiring increasing chargediameter to sustain detonation. Attempts to increase the density, byeither using a denser grade of aluminum or addition of water, alwaysresulted in increasing the critical diameter.

In summary these formulations for underwater explosives have an impactsensitivity that places it among the more-sensitive secondary explosiveson the basis of drop tests. Its thermal stability is extremely high whencompared to other chlorate and perchlorate formulations. In fact it hasgreater thermal stability than even the slurry formulations containingammonium nitrate, water and secondary military approved explosivesensitizers. The ignition sensitivity is very high and sensitivity asindicated by critical diameter and minimum booster criteria, is similarto other multiple-component formulations and is very dependent upondensity. The heat of explosion and available energy is high, but therate of detonation is very low which results in low brisance.

Obviously many modifications and variations of the present invention arepossible in the light of the above teachings. It is therefore to beunderstood that within the scope of the appended claims the inventionmay be practiced otherwise than as specifically described.

5 What is claimed is: 1. An underwater explosive composition consistingessentially of the following ingredients.

Ingredients: Percent by weight Aluminum 18.3 Sulfur 14.6 Potassiumperchlorate 67.1

2. An underwater explosive composition consisting essentially of thefollowing ingredients:

Ingredients: Percent by weight Aluminum 12.09 Red phosphorus 17.11Potassium perchlorate 70.80

67.1% by weight potassium perchlorate having a mesh size of 325; saidexplosive having a density of 1.03 to 1.6 gm./cm.

References Cited UNITED STATES PATENTS 1,253,597 1/1918 Hitt 149422,189,398 2/1940 Hunter 149-42 10 2,478,918 8/1949 Hale et a1. 14937 XOTHER REFERENCES Philadelphia Photographer, Dec. 17, 1887, p. 765.

LELAND A. SEBASTIAN, Primary Examiner.

US. Cl. X.R.

1. AN UNDERWATER EXPLOSIVE COMPOSITION CONSISTING ESSENTIALLY OF THEFOLLOWING INGREDIENTS.
 2. AN UNDERWATER EXPLOSIVE COMPOSITION CONSISTINGESSENTIALLY OF THE FOLLOWING INGREDIENTS: INGREDIENTS: PERCENT BY WEIGHTALUMINUM 12.09 RED PHOSPHOROUS 17.11 POTASSIUM PERCHLORATE 70.80